Does anyone know how much it costs to swap out non black rims for the shadow package rims? And what else would I have to swap on a non shadow package to make it a shadow package looking car?

Which model / age are you referring to ?

Wheels are an easy swap - find some new ones on eBay or similar - just be careful as there's a lot of fakes out there.

After that, it's all the grey / silver trim pieces - only you can decide whether it's worthwhile. If you can be without the car for a few days, then you can take it to a bodyshop who should be able to remove, respray & refit them.

Alternatively, you can buy all the darker pieces & fit them yourself, there's a list of part numbers and more detail on this thread - https://www.fullfatrr.com/forum/topic72659.html

You need to be careful, as pre- and post-face lift have different parts on the front bumper. I still need to remove the front bumper and replace the fins. I am waiting for better weather in the summer and a free weekend to do that.
I am happy with the look. SDV8 AB MY 2020
MINI Cooper S Cabrio
Kit: Jaguar XK140 (in progress - the website is link to build)